Axial backlash in guiding shafts

[nudelmannrichter 14]

Hi folks,

since starting with the UM2 I noticed a bad "klack" sound from time to time that told me that something is not as intendet to be. I took me quite a while staring at different spots of the machine until I was able to locate the source of this.

It is an axial backlash of the right x-moving/y-guiding shaft. It works itself about a mm or so to the front of the machine and then in the right moment if turning and sliding come together in the right way - KLACK - it moves back and the pulley on the back end hits the bearing plate that sits in the backplate.

Ok not as bad as I expected but I dont like such KLACK and backlash moving parts especially as the other shafts do not behave same way and a klacking like this may cause untightening of other parts later.

Has anyone here same experience and did you fix it?

My two ideas are to loosen the back pulley screw a bit, push the pulley back until it touches the bearing plate slightly and to tighten the screw again.

I know that from engineering point of view its not good to fix both sides of a moving shaft to tight but as the whole machine is somehow "elastic" this might not cause problems.

My other idea is to apply a spring loaded device on the outer backside that pushes the shaft insife the machine with a reasonable force so it is not pressed hard but also does not tend to KLACK anymore.

Maybe anyone has some ideas or this helps others to locate a problem

cheers

stefan

 

[illuminarti 18]

See this other thread from today:

http://umforum.ultimaker.com/index.php?/topic/5285-um2-low-quality-prints-due-to-rod-displacement/?p=46825

 

[nudelmannrichter 14]

Thanks for the hint, illuminarti, but maybe what's been described there might not meet the effect I wrote about.

For the moment, this axial movement does not cause bad prints - its more that I think if I let it as it is that it might cause wear off or disadjusting problems in the future. And the KLACK sound is enerving somehow as I had some issues with warping at small overhangs before and when the nozzle came across these it hits the tiny things standing in the way what also causes a bad sound similar to the KLACK. Not as loud and clear but too loud to ignore. And so I would be happy if I could fix this, So if I hear a bad sound in future I would love to be sure that it does not come from backlash or things like that.

I just looked further into the construction and found that also the left shaft hat sich backlash but does not move axial during the print. The 3D file published by Ultimaker shows a distance of exactly 1 mm between bearing and pulley on the back side. The question is if this is wanted or if this will be adjusted to ZERO during assembly. I don't want to build problems into a running machine but if it is something that better should be fixed, I'd like to fix.

thanks and cheers

stefan

 

[illuminarti 18]

The play in the rods isn't causing bad prints in the other thread either. :-) Just do what I talk about in that thread to tighten the pulleys and spacers against the bearings.

[nudelmannrichter 14]

all right, I lost this somehow in the discussion about the effects desribed there.

Ok, you are telling that in general I might do what I wrote in my initial post in this thread.

Thanks again for pushing my nose into it

I will do this and see how it goes.

By the way, do you think the Ultiguys intended to leave one mm space or would you say that the assembling guys normally take care of bringing this axial backlash to zero?

As I am constructing machines in 3D I know that the 3D model and the assembled real machine is not always identical in detail.

cheers

stefan

 

[illuminarti 18]

No, I'm absolutely certain that it's intended that the pulley is tight against the spacer, and the spacer is tight against the bearing. :-)

 

all right, I lost this somehow in the discussion about the effects desribed there.

Ok, you are telling that in general I might do what I wrote in my initial post in this thread.

Thanks again for pushing my nose into it

I will do this and see how it goes.

By the way, do you think the Ultiguys intended to leave one mm space or would you say that the assembling guys normally take care of bringing this axial backlash to zero?

As I am constructing machines in 3D I know that the 3D model and the assembled real machine is not always identical in detail.

cheers

stefan

 

[gr5 2,024]

But not *too* tight.

 

[nudelmannrichter 14]

all right guys, this afternoon I moved the pulleys to make them touch the bearings. So everythings is still moving easily.

Startet a small test print for a different reason and during the first few minutes no KLACK sound - so no backlash anymore.

Thanks for the tips. Think next prints will be more quiet than before. Will have an eye on this, hope the pulley will not move...

cheers

stefan

 

[nudelmannrichter 14]

after a 10hrs print, no klack sound. So thumbs up!

tks guys

stefan